Java checking if list is empty

Finding an ArrayList in Java is Empty or Not

We are going to learn how to check if an ArrayList is empty or not. In order to do that we have several ways.

Below is the java program to know if an ArrayList is empty or not using if else

import java.util.ArrayList; public class arraycheck < public static void main(String args[])< ArrayListlist=new ArrayList(); if(list.size()==0) < System.out.println("Its Empty"); >else System.out.println("Not Empty"); > >

run: Its Empty BUILD SUCCESSFUL (total time: 0 seconds)

Explanation:

We have not inserted anything in our ArrayList. So the size of the list is zero. Thus we are getting “Its Empty” in the output console box.

Here we are comparing our ArrayList size with zero. If there exists any value in our ArrayList the size of the list will be greater than zero.

This time below we are going to add some integer values in our ArrayList below

import java.util.ArrayList; public class arraylistcheck < public static void main(String args[])< ArrayListlist=new ArrayList(); list.add(51); list.add(53); if(list.size()==0) < System.out.println("Its Empty"); >else System.out.println("Not Empty"); > >

run: Not Empty BUILD SUCCESSFUL (total time: 0 seconds)

Using isEmpty() Method:

In Java, we have a method called isEmpty() to check if an ArrayList is empty or not

Below is the same code but this time we are going to use isEmpty() method instead of comparing the size of the ArrayList with zero.

import java.util.ArrayList; public class arraylistcheck < public static void main(String args[])< ArrayListlist=new ArrayList(); list.add(51); list.add(53); if(list.isEmpty()) < System.out.println("Its Empty"); >else System.out.println("Not Empty"); > >

run: Not Empty BUILD SUCCESSFUL (total time: 0 seconds)

import java.util.ArrayList; public class arraylistcheck < public static void main(String args[])< ArrayListlist=new ArrayList(); if(list.isEmpty()) < System.out.println("Its Empty"); >else System.out.println("Not Empty"); > >

run: Its Empty BUILD SUCCESSFUL (total time: 0 seconds)

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Check if an ArrayList is Empty in Java

Learn to check if ArrayList is empty or not using isEmpty() and size() methods. Please note that isEmpty() method also internally check the size of ArrayList.

The ArrayList.isEmpty() method returns true if the list contains no elements. In other words, the method returns true if the list is empty. Else isEmpty() method returns false.

In the given example, we first initialized an empty ArrayList and checked if it was empty. Method returns true because there is nothing inside the list.

ArrayList list = new ArrayList(); Assertions.assertTrue(list.isEmpty());

Then we added an element «A» to list and check again. This time list is not empty, and the method returns false. Now we again cleared the list and checked again. The list is empty again.

list.add("1"); Assertions.assertFalse(list.isEmpty()); list.clear(); Assertions.assertTrue(list.isEmpty());

In application programming, it is advisable to check both if list is not null and then not empty. If list is not initialized, we may get NullPointerException in runtime.

Another way to check if the arraylist contains any element or not, we can check the size of the arraylist. If the list size is greater than zero, then the list is not empty. If the list size is 0, the list is empty.

If we look inside the isEmpty() method, it also checks the size of the arraylist to determine if it is empty.

ArrayList list = new ArrayList(); Assertions.assertTrue(list.size() == 0); list.add("1"); Assertions.assertTrue(list.size() == 1); list.clear(); Assertions.assertTrue(list.size() == 0);

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How to Check if an ArrayList is Empty in Java?

To check if an ArrayList is empty, you can use ArrayList.isEmpty() method or first check if the ArrayList is null, and if not null, check its size using ArrayList.size() method. The size of an empty ArrayList is zero.

ArrayList.isEmpty() – Reference to Syntax and Examples of isEmpty() method.

ArrayList.size() – Reference to Syntax and Examples of size() method.

Example 1 – Check if ArrayList is Empty using ArrayList.isEmpty()

ArrayList.isEmpty() method returns true if the ArrayList is empty, and false if it is not empty.

In the following example, we will create an ArrayList, add no elements to it, and check if it is empty or not by using ArrayList.isEmpty() method.

Java Program

import java.util.ArrayList; public class ArrayListExample < public static void main(String[] args) < ArrayListmyList = new ArrayList(); if(myList.isEmpty()) < System.out.println("ArrayList is empty."); >else < System.out.println("ArrayList is not empty."); >> >

Example 2 – Check if ArrayList is Empty using Size

In the following example, we will create an ArrayList, add no elements to it, and check if it is empty or not by getting the size of the ArrayList.

Java Program

import java.util.ArrayList; public class ArrayListExample < public static void main(String[] args) < ArrayListmyList = new ArrayList(); if(myList==null || myList.size()==0) < System.out.println("ArrayList is empty."); >else < System.out.println("ArrayList is not empty."); >> >

Conclusion

In this Java Tutorial, we learned how to check if an ArrayList is empty or not using ArrayList built-in methods.

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Java Check If List is Empty: Best Practices, Code Examples and More

Learn how to check if a list is empty in Java with examples and best practices. Explore List interface’s isEmpty() method, checking for null values separately, and using Spring framework’s CollectionUtils class.

• Introduction
• Using the List interface’s isEmpty() method
• Checking for null values separately
• Using the Spring framework’s CollectionUtils class
• Other methods to check if a list is empty
• Important points to keep in mind
• Helpful points for Java development
• Additional Java Code Examples for Checking If a List is Empty
• Conclusion
• How to check if ArrayList is empty in Java?
• How do you know if a file is empty in Java?
• How to check if a list is empty or not in Python?
• How to check if a LinkedList is empty in Java?

As a Java developer, checking if a list is empty is an essential task that you will encounter often in your projects. In this post, we will explore the best practices, code examples, and more on how to check if a list is empty in Java.

Introduction

If you are working with lists in Java, it is crucial to check if a list is empty. An empty list is a list that contains no elements. Checking if a list is empty is important because it helps you avoid null pointer exceptions and other potential errors in your code.

In this post, we will cover the different methods and best practices for checking if a list is empty in java . We will use clear and concise explanations and provide code examples to ensure that you have a thorough understanding of the topic.

Using the List interface’s isEmpty() method

The first and simplest method to check if a list is empty is by using the isEmpty() method of the List interface.

The List interface is a part of the Java Collections Framework and is used to store collections of elements. The isEmpty() method returns true if the list contains no elements and false otherwise.

ListString> list = new ArrayList<>();if (list.isEmpty())  System.out.println("The list is empty."); > else  System.out.println("The list is not empty."); > 

Best practices for working with the List interface include initializing the list to an empty list and using the add() method to add elements to the list.

Checking for null values separately

It is important to note that an empty list is not the same as a null list. A null list is a list that has not been initialized and has no memory allocated to it. To check for null values separately, you can use the following code:

ListString> list = null;if (list == null)  System.out.println("The list is null."); > else if (list.isEmpty())  System.out.println("The list is empty."); > else  System.out.println("The list is not empty."); > 

best practices for handling null values in java include initializing variables to a default value and checking for null values before using them.

Using the Spring framework’s CollectionUtils class

If you are using the Spring framework in your Java development, you can use the CollectionUtils class to check for null or empty lists.

The CollectionUtils class is a part of the Spring framework and provides a set of utility methods for working with collections. The isEmpty() method of the CollectionUtils class returns true if the list is null or empty and false otherwise.

ListString> list = new ArrayList<>();if (CollectionUtils.isEmpty(list))  System.out.println("The list is null or empty."); > else  System.out.println("The list is not null or empty."); > 

Best practices for using the Spring framework in Java development include using the appropriate Spring framework components for your project and following the Spring framework conventions.

Other methods to check if a list is empty

There are other methods to check if a list is empty in java , including checking the size of the list and using a for loop to iterate over the list.

To check the size of the list, you can use the size() method of the List interface:

ListString> list = new ArrayList<>();if (list.size() == 0)  System.out.println("The list is empty."); > else  System.out.println("The list is not empty."); > 

To use a for loop to iterate over the list, you can use the following code:

ListString> list = new ArrayList<>();boolean isEmpty = true;for (String element : list)  isEmpty = false; >if (isEmpty)  System.out.println("The list is empty."); > else  System.out.println("The list is not empty."); > 

Best practices for choosing the most appropriate method for a given situation include considering the performance, readability, and maintainability of the code.

Important points to keep in mind

There are important points to keep in mind when checking for empty lists in Java. These include the definition of an empty array and the usage of the BufferedReader and LinkedList classes.

An empty array is an array that has no elements. To check for an empty array in Java, you can use the length property:

int[] array = new int[0];if (array.length == 0)  System.out.println("The array is empty."); > else  System.out.println("The array is not empty."); > 

The BufferedReader and LinkedList classes are also commonly used in Java development. To check if a BufferedReader is empty, you can use the ready() method:

BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));if (!reader.ready())  System.out.println("The BufferedReader is empty."); > else  System.out.println("The BufferedReader is not empty."); > 

To check if a LinkedList is empty, you can use the isEmpty() method:

LinkedListString> list = new LinkedList<>();if (list.isEmpty())  System.out.println("The LinkedList is empty."); > else  System.out.println("The LinkedList is not empty."); > 

Helpful points for Java development

There are helpful points for Java development that are related to checking for empty lists, including the Java Collections Framework, the Stream API, and the Optional class.

The Java Collections Framework is a set of classes and interfaces that provide a way to store and manipulate groups of objects. It includes the List interface that we have already discussed.

The Stream API is a new feature introduced in Java 8 that allows you to process collections of data in a declarative way. You can use the filter() method to check if a list is empty:

ListString> list = new ArrayList<>();if (list.stream().filter(e -> e != null).count() == 0)  System.out.println("The list is empty."); > else  System.out.println("The list is not empty."); > 

The Optional class is a container object that may or may not contain a non-null value. You can use the isEmpty() method of the Optional class to check if the list is empty:

ListString> list = new ArrayList<>();if (Optional.ofNullable(list).isEmpty())  System.out.println("The list is empty."); > else  System.out.println("The list is not empty."); > 

Best practices for using these Java development points include understanding their usage and benefits and using them appropriately in your Java development projects.

Additional Java Code Examples for Checking If a List is Empty

In Java as proof, how to check if a list is empty java code example

if (list != null && !list.isEmpty())

Conclusion

In this post, we have explored the best practices, code examples, and more on how to check if a list is empty in Java. We have covered the different methods and best practices for checking for empty lists, including using the List interface’s isEmpty() method, checking for null values separately, using the Spring framework’s CollectionUtils class, and other methods.

We have also discussed important points to keep in mind when checking for empty lists in Java, including the definition of an empty array and the usage of the BufferedReader and LinkedList classes. Additionally, we have covered helpful points for Java development related to checking for empty lists, including the Java Collections Framework, the Stream API, and the Optional class.

By following these best practices and using the appropriate methods and classes, you can ensure that your Java development projects are error-free and efficient.

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